Such a structural element is known from the EP-A 0 382 060 and is used to line walls and roofs and also for windows and parapets. Especially for the observer located in the building, such structural elements are, however, often not pleasing aesthetically, since the solar cells that are used are virtually opaque.
Furthermore, it is desirable that the structural or facade elements provide a high acoustical and thermal insulation. In addition, known structural elements provide a vacuum in the space between the outside plate sandwich and the internal plate or also introduce an inert gas for absorbing the thermal radiation. To prevent the radiation of heat into the interior of the building, a low E coating is applied as a heat insulating layer on the inner surface of the inner plate. These measures bring about heat transfer values as low as 1.3 W/m.sup.2 K, moreover as a function of the dimensions of the structural element, especially the distance between the inner plate of the sandwich and the other internal plate.
The object of the invention is to provide a structural element that is aesthetically appealing from the outside and inside, has a high acoustical and thermal insulation, and can be manufactured simply and economically.
According to the invention, the solar cells are embedded in a layer of casting resin; furthermore, the inner plate recedes in its dimensions in the region of at least one edge at least partially with respect to the corresponding edge of the outer plate and forms thus a recess that also reaches over the layer of casting resin and through which the necessary electrical lines for the solar cells are guided, whereby the recess in the direction of the interior of the structural element is covered by the spacing frame and the interior seal.
As an alternative, the outer plate recedes in its dimensions in the region of at least one edge at least partially with respect to the corresponding edge.
Embedding the solar cells in a layer of casting resin produces a sandwich that is not only economical to manufacture but also is characterized by the fact that the solar cells are held absolutely stable in position. The stepped design of the plates of the plate sandwich makes it possible to lead the electrical lines in a simple and reliable manner out of the structural element. Since the step is covered by the spacers that are necessary in any event, the overall aesthetic effect of the structural element is not impaired. An especially suitable casting resin is a well-known highly transparent sound proof casting resin based on acrylate. Since good sound proofing properties also coincide usually with good heat insulating properties, with these measures alone a very good insulated structural element is obtained.
It is advantageous to supplement the internal plate with a second plate having an intermediate layer of sound proof casting resin, forming an inside plate sandwich. In this manner, not only the insulating properties that were good in any event are improved. If a light scattering sound proof casting resin is used, this causes a frosted glass effect, thus preventing the view from the interior of the building of the back side of the solar cells in the exterior sandwich. The same effect is obtained, if when using the internal plate alone this internal plate is made of frosted glass or if in the case of the inside plate sandwich at least one of the plates is frosted.
Solar cells, whose maximum absorption preferably for sunlight lies in a spectral range that differs from that of the solar cells of the outside plate sandwich, can also be embedded into the intermediate layer. Logically the solar cells of the inside plate sandwich are offset relative to those of the outside plate sandwich. It is also recommended that the electrical lines for this second solar cell arrangement be led in the same or similar manner out of the plate sandwich as already explained for the outside plate sandwich. In such an embodiment the plate of the inside plate sandwich that is arranged in the direction of the building interior will be frosted.
The outer plate of the external plate sandwich is made preferably of at least in part chemically or thermally prestressed glass, where a flint glass that is poor in iron has proven to be especially suitable. An outer plate made of plastic is also conceivable, where the security against fracture is increased. Together with the highly transparent layer of casting resin, high transparency is ensured, so that no only the solar cells of the outside plate sandwich but also optionally those of the inside plate sandwich can contribute optimally to the harnessing of energy.
The thermal insulation is further improved if the space between the outside sandwich and the internal plate is filled with a gas of low thermal conductivity, for example with dried air, with sulfur hexafluoride or with a mixture of these media.
For the configuration of the solar cells the possibilities are virtually unlimited. With respect to an optimal harnessing of energy it is advantageous to configure the solar cells of the outside plate sandwich in such a manner that the plate surface is substantially covered. In so doing, the outer regions of the plate sandwich are excluded in which the casting resin located there exclusively fixes in position the outer plate and the inner plate.
As solar cells, polycrystalline or amorphous solar cells can be used, where in each plate sandwich one type of solar cell or a combination of both types of solar cells is embedded. The solar cells are arranged advantageously on the casting resin side on the surface of the plates, a feature that is suitable especially for amorphous thin layer solar cells.
If amorphous thin layer solar cells, which exhibit an extensive transparency for light in the visible range, are provided at least in the outside plate sandwich, the aesthetic impression of the facade element is further improved, but losses in the obtainable energy must be accepted. On the whole, the structural element according to the invention has the advantage of especially high transparency, if a specially designed light scattering layer is provided.
If only the outside plate sandwich is provided, the irradiation of the infrared portion of the solar spectrum can be prevented by applying a solar insulating coating on the inner plate relative to the space between the outside sandwich and the internal plate.
In each of the described embodiments a thermal protective coating can also be applied on the internal plate.
To cover the solar cells in the direction of the building interior, a surface imprinting can be applied to the surface of the plates.
Suitable material for the inner plate and optionally the plates of the inside plate sandwich is normal prestressed glass. Within the inventive idea, structural elements of the invention can also be used in framed format--optionally from a production point of view.
In the following the invention shall be described by means of examples with the aid of the accompanying drawings.